Lepus 0.62X Telecompressor Lens

The
Optec Lepus 0.62X is a 4-element telecompressor designed
by Optec engineers to work with newer, well-corrected Schmidt-Cassegrain telescopes
such as the Meade ACF and the Celestron
EdgeHD series telescopes. Also known as a focal-reducer, the Lepus
provides a 0.62X reduction of the telescope's effective focal length. Lepus works well with most mid-size CCD cameras and Digital SLR cameras
having sensor diagonals up to 28mm.

Designed for Corrected Schmidt-Cassegrain Telescopes

Optec'sNextGEN series of telecompressors
were designed to correct the coma inherent in the classic
Schmidt-Cassegrain Telescope (SCT). With optical design
improvements by Meade and Celestron, the NextGen series would
overcorrect for coma and therefore became unsuitable for use with the
ACF and EdgeHD optics. Additionally, image sensors were increasing
in size and the addition of filter wheels, off-axis guiders, and
adaptive optics units required more back-focus distance between
telecompressor and camera.

Lepus is optimized
for 100mm of distance between the last lens surface and the image plane.
Measured from the telecompressor flange, this distance works out to
105mm as shown at left. Assuming a native focal ratio of f/10,
the Lepus 0.62X will reduce the effective focal ratio to approximately
f/6.2. Shifting the image plane outward will provide additional
reduction but a loss of star quality at the edge of the images.
The optimal distance for most SCT's is 100mm with the exception of the
C9.25 EdgeHD SCT.

Designed for Midsize CCD's and DSLR's

Lepus can will deliver a fully unvignetted image
22mm in diameter, but will provide well-corrected images out to 28mm
with a small amount of light fall-off. Flat fielding is
recommended for best results. See Optec's line of
Alnitak flat-fielding devices for
additional details.

The
NGC2818 image at left was provided by Ronny Kaplanian
and taken with his Celestron C9.25 EdgeHD, Lepus-HD C9.25 Edition
telecompressor, and his Starlight Xpress SXVR-M25C camera in a
monochrome mode with separate RBG filtered images.
The image sensor on the SXVR-M25C measures 23.5mm x 15mm for a diagonal measurement of
nearly 28mm. The image was combined and further processed by Terry Hancock with only
slight cropping to remove the stacking artifacts. Click
here for a full size image in pdf format.

Image courtesy Ronny Kaplanian. Processing by
Terry Hancock.

Astronomy Technology Today
Review

Klaus Brasch reviewed the Lepus-HD C11 Edition
telecompressor with his Celestron EdgeHD C11 telescope for the January
2012 issue of Astronomy Technology Today.

Dr. Brasch writes "The Lepus
telecompressor is light weight, well made
and yielded pin-point stars across the entire
image."

Read the full report at the Astronomy Technology Today website or
click the image at right.

Telescope-Specific Editions:

The Lepus telecompressor lens design is available in several
editions for a number of popular Corrected Schmidt-Cassegrain
Telescopes.

#19405 - Lepus-STL 0.62X
with STL camera-side thread is a special edition designed to fit
directly into the STL 2.156"x24tpi female thread on the SBIG
STT8300-FW8G-AO8 camera. The camera side thread can also be attached to
the camera with a special STL-camera fixed length camera mount or the
new VLC mounts.

#19407 - Lepus 0.62X Standard Edition
fits into any 2-inch focuser and works especially well with the
Meade f/10 and f/8 ACF Coma-Free Schmidt-Cassegrain Telescopes.
Camera mounts are available in fixed and variable lengths.

#19410 - Lepus HD C9.25 EdgeHD Edition is mounted into a
3.25"x24tpi thread for direct attachment to Celestron 9.25" EdgeHD SCT. The mount is close-coupled to
the telescope OTA and have a shorter back-focus to maintain optimal image quality.